4.3tbi to 7.4tbi 4l80e swap vss issue.

Hello I have a issue with my truck that I have been trying to figure out for about a year now. I have a 1993 Chevrolet 2WD C2500 truck with a 4.3L TBI in it and a 4l60e (I think). I swapped to a 1994 7.4L tbi 4l80e 4WD. I drove this donor truck before I took everything out. So all I had to do was change the output shaft to work with 2wd and my drive shaft witch I did. I used the donor Engine,Wire harness, Transmission and PCM. Both these trucks have the 7060 PCM. I had a reluctor ring and VSS sensor added to the 4l80e for 2wd use. My issue is that I am getting is the PCM is not picking up the output shaft speed (VSS error). I tried 2 other sensors and I get the samething. BUT when I put the 4.3 tbi PCM in the transmission shifts perfectly just no OD and the engine runs like crap. Is there something I am missing? Is it having a issue because it was originally 2wd? With the 7.4 TBI ecm the engine runs amazing but goes into limp mode.